This application claims benefit of Japanese Patent Application No. 2000-348871 filed on Nov. 16, 2000, the contents of which are incorporated by the reference.
The present invention relates to array waveguide grating, optical transmitter and optical communication system with a monitoring function for monitoring signal.
In a DWDM (Dense Wavelength Division Multiplexing) system, for example, alive monitoring and level equalization of signal are required. Accordingly, in such a system couplers or like tapping devices are heretofore provided before or after an AWG (arrayed waveguide grating) to branch signal and monitor the branched signal so as to meet the requirements.
FIG. 25 shows a summary of a prior art synthesizer using a taping device. Signals 1011 to 101N of individual wavelengths are inputted to an arrayed waveguide grating 102, and outputted as resultant wavelength multiplexed signal 103 therefrom. On the input side of the arrayed waveguide grating 102, tapping devices 1041 to 104N are provided in correspondence to the individual wavelengths for branching the signal to obtain monitoring signals 1051 to 105N.
In the system using the above synthesizer or array waveguide grating, since the tapping devices 1041 to 104N are used for branching signal, it is necessary to prepare such components as couplers and optical fibers for connecting the couplers in number corresponding to the number of monitoring channels. Therefore, with increase of the channel number the number of components necessary for the monitoring is increased, thus leading to size increase of the arrayed waveguide grating as a whole. In addition, the increase of the number of components leads to device cost increase.
Accordingly, Japanese Patent Laid-Open No. 9-49937 proposes an arrayed waveguide grating, in which N input waveguides for wavelength monitoring are provided in addition to N input waveguides for signal inputting, and also output waveguides for wavelength monitoring are provided each for each side of the N output waveguides.
FIG. 26 shows the construction of this arrayed waveguide grating. As shown, on a substrate 111 are formed N input waveguides 112 for signals, N input waveguides 113 for wavelength monitoring signals, a waveguide array 114 of M waveguides having progressively increasing length with a predetermined waveguide length difference xcex94L, N output waveguides 115, output waveguides 116 and 117 for wavelength monitoring each provided on each side of the output waveguides 115, an input side slab-waveguide inter-connecting the two pairs input waveguides 112 and 113 and the waveguide array 114, and an output side slab-waveguide 119 inter-connecting the waveguide array 114 and the three pairs of output waveguides 115 to 117.
In the proposed array waveguide grating, the N input waveguides 112 connected to the slab-waveguide 118 and the N output waveguides 115 connected to the output side slab-waveguide 119 are used for the signals, while the N input waveguides 113 connected to the input side slab-waveguide 116 and the output waveguides 116 and 117 for wavelength monitoring connected to the output side slab-waveguides 119 are used for the waveguide monitoring. This waveguide grating, therefore, has a drawback that monitoring with the actual signals is impossible.
An object of the present invention, therefore, is to provide arrayed waveguide grating, optical transmission system and optical communication system, which permits using actual signals to be multiplexed for monitoring these signals and suppressing system size and cost increase as much as possible.
According to a first aspect of the present invention, there is provided an arrayed waveguide grating having a slab-waveguide, the slab-waveguide comprising: a plurality of input ports for inputting signals of different wavelengths in correspondence to these wavelengths; an output port disposed on the focus position of the 0-th order diffraction beams inputted from the input ports for outputting a signal obtained as a result of multiplexing of the individual wavelengths; and a monitor signal port disposed on the focus position of higher order diffraction beams other than the 0-th order obtained from the signals inputted from the input ports for monitoring the multiplexed signal.
In this invention, while outputting the 0-th order diffraction beams obtained from the signals inputted to the slab-waveguide of the arrayed waveguide grating from the output port, the monitor signal port is provided at the focus position of higher order diffraction beams other than the 0-th order, for instance, the 1-st order diffraction beams, for monitoring the wavelength multiplexed signal by using this port.
According to a second aspect of the present invention, there is provided an arrayed waveguide grating having a slab-waveguide, the slab-waveguide comprising: a plurality of input ports for inputting signals of different wavelengths in correspondence to these wavelengths; an output port disposed on the focus position of the 0-th order diffraction beams inputted from the input ports for outputting a signal obtained as a result of multiplexing of the individual wavelengths; and a higher order diffraction beam reflecting means disposed on the focus position of higher order diffraction beams other than the 0-th order obtained from the signals inputted from the input ports for reflecting the higher order diffraction beams to the side of the plurality of input ports.
In this invention, while outputting the 0-th order diffraction beams obtained from the signals inputted to the slab-waveguide of the arrayed waveguide grating, a higher order diffraction beam reflecting means is disposed at the focus position of higher order diffraction beams other than the 0-th order, for instance, the 1-st order diffraction beams, for returning the wavelength multiplexed signal to the side of the input ports. Thus, it is possible to monitor the signals of the different wavelengths obtained as a result of demultiplexing of the signal passed in the reverse direction through the arrayed waveguide grating on the input side thereof.
According to a third aspect of the present invention, there is provided an arrayed waveguide grating having a slab-waveguide, the slab-waveguide comprising: a plurality of input ports for inputting signals of different wavelengths in correspondence to these wavelengths; an output port disposed on the focus position of the 0-th order diffraction beams inputted from the input ports for outputting a signal obtained as a result of multiplexing of the individual wavelengths; a higher order diffraction beam reflecting means disposed on the focus position of higher order diffraction beams other than the 0-th order obtained from the signals inputted from the input ports for reflecting the higher order diffraction beams to the side of the plurality of input ports; and one or more monitor signal ports disposed at a position or positions other than the plurality of input ports for taking out a signal or signals reflected from the higher order diffraction beam reflecting means.
In this invention, while outputting the 0-th order diffraction beams of the signals inputted to the slab-waveguide of the arrayed waveguide grating, a higher order diffraction beam reflecting means is disposed at the focus position of higher order diffraction beams other than the 0-th order, for instance the 1-st order diffraction beams, for returning the wavelength multiplexed signal to the side of the input ports. On the input side, one or more monitor signal ports are disposed, and thus a monitor signal or monitor signals can be obtained from the monitor signal port or ports.
According to a fourth aspect of the present invention, there is provided an optical transmission system comprising: an output side slab-waveguide including, a plurality of signal sources each provided for each individual wavelength, an input waveguide for inputting signals of different wavelengths from these signal sources in correspondence to these wavelengths, a channel waveguide array having waveguides with lengths progressively increasing by a predetermined waveguide length difference, an input side slab-waveguide inter-connecting the input side of the channel waveguide array and the input waveguide, and an output port connected to the output side of the channel waveguide array and disposed at the focus position of the 0-th order diffraction beams inputted from the input waveguides through the input side slab-waveguide and the channel waveguide array for outputting a wavelength multiplexed signal; an output waveguide connected to the output port for outputting the multiplexed signal to be transmitted; a monitor signal separating means for demultiplexing, by using the channel waveguide array, the multiplexed signal obtained in the output side slab-waveguide at the focus position of higher order diffraction beams other than the 0-th order obtained from the signals from the input waveguide, thereby separating the monitor signals of wavelengths corresponding to those of the signals inputted from the input waveguides; an output level detecting means for detecting, from the signals of different wavelengths obtained from the monitor signal separating means, the output levels of the individual wavelength signals from the plurality of signal sources; and a signal source power control means for controlling the power levels of the plurality of signal sources according to the output levels of the individual wavelength signals from the plurality of signal sources as detected by the output level detecting means.
In this invention, while outputting the wavelength multiplexed signal for transmission from the output waveguide, the monitor signal separating means demultiplexes, by using the channel waveguide array, the wavelength multiplexed signal obtained in the output side slab-waveguide at the focus position of higher order diffraction beams other than the 0-th order obtained from the signals from the input waveguide, thereby separating monitor signals of wavelengths corresponding to those of the signals inputted from the input waveguides. The output levels of the signals of the different wavelengths corresponding to those of the plurality of signal sources are detected from the separated individual wavelength signal signals, and the power levels of the plurality of the signal sources are controlled according to the detected output levels of the different wavelength signals of the plurality of signal sources.
According to a fifth aspect of the present invention, there is provided an optical transmission system comprising: a plurality of signal sources each provided for each individual wavelength; an input waveguide for inputting signals of different wavelengths from these signal sources in correspondence to these wavelengths; a channel waveguide array having waveguides with lengths progressively increasing by a predetermined waveguide length difference; an input side slab-waveguide inter-connecting the input side of the channel waveguide array and the input waveguide; an output side slab-waveguide including an output port connected to the output side of the channel waveguide array and disposed at the focus position of the 0-th order diffraction beams inputted from the input waveguides through the input side slab-waveguide and the channel waveguide array for outputting a wavelength multiplexed signal and a monitor signal port disposed at the focus position of higher order diffraction beams other than the 0-th order obtained from the signals inputted from the input waveguide; an output waveguide connected to the output port for outputting the multiplexed signal to be transmitted; a monitor signal separating means for demultiplexing, by using the channel waveguide array, the individual wavelength monitor signals from the wavelength multiplexed signal obtained from the monitor port; an output level detecting means for detecting, from the signals of individual wavelengths obtained from the monitor signal separating means, the output levels of the individual wavelength signal signals from the plurality of signal sources; and a signal source power control means for controlling the power levels of the plurality of signal sources according to the output levels of the individual wavelength signals from the plurality of signal sources as detected by the output level detecting means.
In this invention, while outputting the wavelength multiplexed signal for transmission from the output waveguide, the monitor signal separating means separates the higher order diffraction beam signals other than the 0-th order obtained from the signals inputted from the input waveguides from the monitor signal port disposed on the output side slab-waveguide at the focus position of the diffracted signals. The obtained wavelength multiplexed signal is demultiplexed by using the channel waveguide array to obtain the monitor signals of the individual wavelengths. The output levels of the individual wavelength signals of the plurality of signal sources are detected from the obtained signals of the individual wavelengths, and the power levels of the plurality of signal sources are controlled according to the detected output levels of the individual wavelength signals of the plurality of signal sources.
According to a sixth aspect of the present invention, there is provided an optical transmission system comprising: an input waveguide for inputting signals of different wavelengths in correspondence to these wavelengths; a channel waveguide array having waveguides with lengths progressively increasing by a predetermined waveguide length difference; an input side slab-waveguide inter-connecting the input side of the channel waveguide array and the input waveguide; an output side slab-waveguide including an output port connected to the output side of the channel waveguide array and disposed at the focus position of the 0-th order diffraction beams inputted from the input waveguides through the input side slab-waveguide and the channel waveguide array for outputting a wavelength multiplexed signal; an output waveguide connected to the output port for outputting the multiplexed signal to be transmitted; a monitor signal separating means for demultiplexing, by using the channel waveguide array, the multiplexed signal obtained at the focus position of higher order diffraction beam other than 0-th order of the multiplexed signals inputted from the input waveguide in the output slab-waveguide to obtain the individual wavelength monitor signals; an output level detecting means for detecting, from the signals of individual wavelengths obtained from the monitor signal separating means, the output levels of the individual wavelength; and a signal incidence level control means for controlling the incidence levels of the individual wavelength signals incident on the plurality of input waveguides according to the output levels of the individual wavelength signals as detected by the output level detecting means.
In this invention, while outputting the wavelength multiplexed signal for transmission from the output waveguide, the monitor signal separating means demultiplexes, by using the channel waveguide array, the wavelength multiplexed signal obtained in the output side slab-waveguide at the focus position of the higher order diffraction beam signals other than the 0-th order obtained from the signals obtained from the input waveguides, thus obtaining the monitor signals of the individual wavelengths. The output levels of the individual wavelength signals of the plurality of signal sources are detected from the obtained signal signals of the individual wavelengths, and the power levels of the plurality of signal sources are controlled according to detected output levels of the individual wavelength signals of the plurality of signal sources. This case of the invention is applicable not only to the signals obtained from the signal sources but also to relayed signals.
According to a seventh aspect of the present invention, there is provided an optical transmission system comprising: a plurality of input waveguides for inputting signals of different wavelengths in correspondence to these wavelengths; a channel waveguide array having waveguides with lengths progressively increasing by a predetermined waveguide length difference; an input side slab-waveguide inter-connecting the input side of the channel waveguide array and the input waveguide; an output side slab-waveguide including an output port connected to the output side of the channel waveguide array and disposed at the focus position of the 0-th order diffraction beams inputted from the input waveguides through the input side slab-waveguide and the channel waveguide array for outputting a wavelength multiplexed signal and a monitor signal port disposed at the focus position of higher order diffraction beams other than the 0-th order obtained from the signal inputted from the input waveguide; an output waveguide connected to the output port for outputting the multiplexed signal to be transmitted; a monitor signal separating means for demultiplexing or separating, by using the channel waveguide array, the wavelength multiplexed signal obtained from the monitor port to obtain the individual wavelength monitor outputs; an output level detecting means for detecting, from the signals of individual wavelengths obtained from the monitor signal separating means, the output levels of the individual wavelength; and a signal incidence control means for controlling the incidence levels of the individual wavelength signals incident on the plurality of input waveguides according to the output levels of the individual wavelength signals as detected by the output level detecting means.
In this invention, while outputting the wavelength multiplexed signal for transmission from the output waveguide, the monitor signal separating means separates the higher order diffraction beam signals other than the 0-th order obtained from the signals inputted from the input waveguides from the output port disposed in the output side slab-waveguide at the focus position of the diffracted beams. The wavelength multiplexed signal thus obtained is demultiplexed by using the channel waveguide array to obtain the monitor signals of the individual wavelengths. The output levels of the signals of the individual wavelengths are detected from the obtained individual wavelength signals, and the power levels of the plurality of signal sources are controlled according to the detected output levels of the individual wavelength signals. This case of the invention is applicable not only to the signals obtained from the signal sources but also to relayed signals.
According to an eighth aspect of the present invention, there is provided an optical transmission system comprising: an input waveguides for inputting signals of different wavelengths in correspondence to these wavelengths; a channel waveguide array having waveguides with lengths progressively increasing by a predetermined waveguide length difference; an input side slab-waveguide inter-connecting the input side of the channel waveguide array and the input waveguide; an output side slab-waveguide, including an output port connected to the output side of the channel waveguide array and disposed at the focus position of the 0-th order diffraction beams inputted from the input waveguides through the input side slab-waveguide and the channel waveguide array for outputting a wavelength multiplexed signal; an output waveguide connected to the output port for outputting the multiplexed signal to be transmitted; and a monitor signal separating means for demultiplexing or separating, by using the channel waveguide array, the multiplexed signal obtained at the focus position of higher order diffraction beam other than 0-th order of the multiplexed signals inputted from the input waveguide in the output slab-waveguide to obtain the individual wavelength monitor signal outputs.
In this invention, the wavelength multiplexed signal obtained in the output side slab-waveguide at the focus position of the higher order diffraction beam signals other than the 0-th order obtained from the signals inputted from the input waveguides are demultiplexed, thus obtaining the monitor signals of the individual wavelengths.
According to a ninth aspect of the present invention, there is provided an arrayed waveguide grating comprising: an input waveguides for inputting signals of different wavelengths in correspondence to these wavelengths; a channel waveguide array having waveguides with lengths progressively increasing by a predetermined waveguide length difference; an input side slab-waveguide inter-connecting the input side of the channel waveguide array and the input waveguides and having monitor signal ports for monitoring signals returning from the channel waveguide array; an output side slab-waveguide including an output side slab-waveguide including an output port connected to the output side of the channel waveguide array and disposed at the focus position of the 0-th order diffraction beams inputted from the input waveguides through the input side slab-waveguide and the channel waveguide array for outputting a wavelength multiplexed signal and a signal returning means for causing a signal converged on the focus position of higher order diffraction beams other than the 0-th order obtained from the signals inputted from the input waveguides to return from the focus position to the input side; and an output waveguide connected to the output port for obtaining the multiplexed signal.
In this invention, the output side slab-waveguide includes the output port for outputting the wavelength multiplexed signal signals at the focus position of the 0-th diffraction beams inputted from the input waveguides and a signal returning means for returning the signal is converged on the focus position of the higher order diffraction beams other than the 0-th order inputted from the input waveguides from the focus position to the input side, and the monitor signal returned through the channel waveguide array to the input side slab-waveguide is taken out from the monitor signal.
According to a tenth aspect of the present invention, there is provided the arrayed waveguide grating according to the ninth aspect, wherein the signal returning means is a reflecting means disposed at the focus position of higher order diffraction beams other than the 0-th order obtained from the signals inputted from the input waveguides for reflecting the higher order diffraction beams to the side of the plurality of input waveguides.
In this invention, a reflecting means such as a mirror is used as the signal returning means.
According to an eleventh aspect of the present invention, there is provided an arrayed waveguide grating comprising: a substrate; input waveguides disposed on the substrate for inputting signals of individual wavelengths in correspondence thereto; a channel waveguide grating disposed on the substrate and having waveguides with lengths progressively increasing by a predetermined waveguide length difference; an input side slab-waveguide disposed on the substrate and inter-connecting the input side of the channel waveguide array and the input waveguides; an output side slab-waveguide connected to the output side of the channel waveguide array and disposed at the focus position of the 0-th diffraction beams obtained from the signals inputted from the input waveguides through the input side slab-waveguide and the channel waveguide array for outputting a wavelength multiplexed signal and a monitor signal port disposed at the focus position of higher order diffraction beams other than the 0-th order obtained from the signals inputted from the input waveguides; an output waveguide connected to the output port; a waveguide disposed on the substrate and having one terminal connected to the monitor signal port of the output side slab-waveguide and the other terminal disposed on the inner side of one end face of the substrate; and a reflecting means disposed at the other terminal of the waveguide for reflecting the signal led out from the monitor signal port.
In this invention, the monitor signal taken out from the output waveguide is reflected and returned by the reflecting means such as a mirror provided on the waveguide on the substrate.
According to a twelfth aspect of the present invention, there is provided an arrayed waveguide rating comprising: a substrate; input waveguides disposed on the substrate for inputting signals of individual wavelengths in correspondence thereto; a channel waveguide grating disposed on the substrate and having waveguides with lengths progressively increasing by a predetermined waveguide length difference; an input side slab-waveguide disposed on the substrate and inter-connecting the input side of the channel waveguide array and the input waveguides; an output side slab-waveguide connected to the output side of the channel waveguide array and having a wavelength multiplexed signal output port disposed at the focus position of the 0-th diffraction beams obtained from the signals inputted from the input waveguides through the input side slab-waveguide and the channel waveguide array, a monitor signal output port disposed at the focus position of the 0-th order diffraction beams obtained from the signals inputted from the input waveguides and a monitor signal input port for outputting an output from a predetermined path, through which the signal outputted from the monitor signal output port returns, toward the plurality of input waveguides; an output waveguide connected to the output port; and a waveguide disposed on the substrate and optically connecting the monitor signal output port and monitor signal input port.
In this invention, the monitor signals taken out from the output waveguide is returned by the waveguide itself on the substrate.
According to a thirteenth aspect of the present invention, there is provided an arrayed waveguide grating comprising: a substrate; input waveguides disposed on the substrate for inputting signals of individual wavelengths in correspondence thereto; a channel waveguide grating disposed on the substrate and having waveguides with lengths progressively increasing by a predetermined waveguide length difference; an input side slab-waveguide disposed on the substrate and inter-connecting the input side of the channel waveguide array and the input waveguides; an output side slab-waveguide connected to the output side of the channel waveguide array and having a wavelength multiplexed signal output port disposed at the focus position of the 0-th diffraction beams obtained from the signals inputted from the input waveguides through the input side slab-waveguide and the channel waveguide array, and a monitor signal port disposed at the focus position of the 0-th order diffraction beams obtained from the signals inputted from the input waveguides; an output waveguide connected to the output port; a waveguide disposed on the substrate and having one terminal connected to the monitor signal port of the output side slab-waveguide and the other terminal disposed on one end face of the substrate; and a reflecting means disposed on the other terminal of the waveguide for reflecting the signal led out from the monitor signal port.
In this invention, the monitor signal taken out from the output waveguide is led through the waveguide up to the end face of the substrate, and then returned by the reflecting means disposed on this end face.
According to a fourteenth aspect of the present invention, there is provided an arrayed waveguide grating comprising: a substrate; input waveguides disposed on the substrate for inputting signals of individual wavelengths in correspondence thereto; a channel waveguide grating disposed on the substrate and having waveguides with lengths progressively increasing by a predetermined waveguide length difference; an input side slab-waveguide disposed on the substrate and inter-connecting the input side of the channel waveguide array and the input waveguides; an output side slab-waveguide connected to the output side of the channel waveguide array and having a wavelength multiplexed signal output port disposed at the focus position of the 0-th diffraction beams obtained from the signals inputted from the input waveguides through the input side slab-waveguide and the channel waveguide array, a monitor signal output port disposed at the focus position of the 0-th order diffraction beams obtained from the signals inputted from the input waveguides and a monitor signal input port for outputting an output from a predetermined path, through which the signal outputted from the monitor signal output port returns, toward the plurality of input waveguides; a monitor signal output waveguide disposed on the substrate and having one terminal connected to the monitor signal port of the output side slab-waveguide and the other terminal disposed on one end face of the substrate; a monitor signal input waveguide disposed on the substrate and having one terminal connected to the monitor signal input port in the output side slab-waveguide and the other terminal disposed at a position other than the afore-mentioned predetermined position on the end face of the substrate; and an optical fiber for optically inter-connecting the monitor signal output waveguide at one end of the substrate and the corresponding terminal of the monitor signal input waveguide.
In this invention, the monitor signal taken out from the output waveguide is led through the output waveguide up to the end face of the substrate, so that it is inputted to the optical fiber connected to the end face from one terminal of the optical fiber and thence returned through the substrate end face and the monitor signal input waveguide to the output side slab-waveguide.
According to a fifteenth aspect of the present invention, there is provided an arrayed waveguide grating comprising: a substrate; input waveguides disposed on the substrate for inputting signals of individual wavelengths in correspondence thereto; a channel waveguide grating disposed on the substrate and having waveguides with lengths progressively increasing by a predetermined waveguide length difference; an input side slab-waveguide disposed on the substrate and inter-connecting the input side of the channel waveguide array and the input waveguides; an output side slab-waveguide connected to the output side of the channel waveguide array and having a wavelength multiplexed signal output port disposed at the focus position of the 0-th diffraction beams obtained from the signals inputted from the input waveguides through the input side slab-waveguide and the channel waveguide array, and a monitor signal port disposed at the focus position of the 0-th order diffraction beams obtained from the signals inputted from the input waveguides; an output waveguide disposed on the substrate and having one terminal connected to the monitor signal port of the output side slab-waveguide and the other terminal disposed on a predetermined position of the substrate; an optical fiber having one terminal connected to the afore-mentioned other terminal of the output waveguide located on the end face of the substrate; and a reflecting means connected to the other terminal of the optical fiber for reflecting the signal led out from that other terminal.
In this invention, the monitor signal taken out from the output waveguide is led through the output waveguide up to the end face of the substrate and inputted to the optical fiber connected to the end face from one terminal of the optical fiber. The other terminal of the optical fiber is connected to the reflecting means reflecting the signal led from one end of the optical fiber. Thus, it is possible to return the wavelength multiplexed monitor signal to the output side slab-waveguide.
According to a sixteenth aspect of the present invention, there is provided an arrayed waveguide grating comprising: input waveguides for inputting signals of individual wavelengths in correspondence to these wavelengths; a channel waveguide array having waveguides with lengths progressively increasing by a predetermined waveguide length difference; a feedback waveguide for feeding back a multiplexed signal monitor signal; an input side slab-waveguide, in which the input waveguides and the feedback waveguide are disposed on one side and the input side of the channel waveguide array is disposed on the output side; an output side slab-waveguide connected to the output side of the channel waveguide array and having an output port disposed on the focus position of the 0-th diffraction beams obtained from the signal inputted from the input waveguides through the input side slab-waveguide and the channel waveguide array for outputting the wavelength multiplexed signal, a feedback port disposed at the focus position of higher order diffraction beams other than the 0-th order obtained from the signals inputted from the input waveguides and one or monitor signal ports for outputting monitor signals separated from the multiplexed signal inputted from the feedback waveguide to the channel waveguide array; an output waveguide connected to the output port of the output side slab-waveguide; and monitor signal output waveguide connected to the monitor signal port.
In this invention, the wavelength multiplexed monitor signal obtained from the feedback port of the output side slab-waveguide, is inputted to the input side of the input side slab-waveguide by using the feedback waveguide. Thus, the monitor signal can be demultiplexed through the channel waveguide array and taken out from the monitor signal port of the output side slab-waveguide.
According to a seventeenth aspect of the present invention, there is provided an arrayed waveguide grating comprising: input waveguides for inputting signals of individual wavelengths in correspondence to these wavelengths; a channel waveguide array having waveguides with lengths progressively increasing by a predetermined waveguide length difference; a feedback fiber for feeding back a multiplexed signal monitor signal; an input side slab-waveguide, in which the input waveguides and the feedback fiber are disposed on one side and the input side of the channel waveguide array is disposed on the output side; an output side slab-waveguide connected to the output side of the channel waveguide array and having an output port disposed on the focus position of the 0-th diffraction beams obtained from the signal is inputted from the input waveguides through the input side slab-waveguide and the channel waveguide array for outputting the wavelength multiplexed signal, a feedback port disposed at the focus position of higher order diffraction beams other than the 0-th order obtained from the signals inputted from the input waveguides and one or monitor signal ports for outputting monitor signals separated from the multiplexed signal inputted from the feedback waveguide to the channel waveguide array; an output waveguide connected to the output port of the output side slab-waveguide; and monitor signal output waveguide connected to the monitor signal port.
In this invention, the wavelength multiplexed monitor signal obtained from the feedback port of the output side slab-waveguide, is inputted to the input side of the input side slab-waveguide by using the feedback fiber. Thus, the monitor signal can be demultiplexed through the channel waveguide array and taken out from the monitor signal port of the output side slab-waveguide.
According to an eighteenth aspect of the present invention, there is provided an arrayed waveguide grating comprising: input waveguides for inputting signals of individual wavelengths in correspondence to these wavelengths; monitor waveguides disposed at positions individual from the input waveguides for outputting monitor signals; a channel waveguide array having waveguides with lengths progressively increasing by a predetermined waveguide length difference; an output side slab-waveguide connected to the output side of the channel waveguide array and including a signal returning means for causing a signal converged on the focus position of higher order diffraction beams other than the 0-th order obtained from the signals inputted from the input waveguides through the input side slab-waveguide and the channel waveguide array to return from he focus position to the input side; an input side slab-waveguide inter-connecting the input waveguides, the monitor waveguides and the input side of the channel waveguide array for outputting the signal inputted from the output side slab-waveguide to the channel waveguide array to the monitor signal waveguide; an output port disposed on the output side slab-waveguide at the focus position of the 0-th diffraction beams obtained from the signal inputted from the input waveguides for outputting the wavelength multiplexed signal; and an output waveguide connected to the output port.
In this invention, the monitor signal waveguide is connected in addition to the input waveguides for inputting signals to be multiplexed to the input side of the slab-waveguide. The output side slab-waveguide includes the signal returning means for taking out returned on the input side slab-waveguide side from the monitor signal waveguide. The returned monitor signal is obtained from the port other than the input waveguides (the port being deviated in position from the input waveguides).
According to a nineteenth aspect of the present invention, there is provided the arrayed waveguide grating according to the eighteenth aspect, wherein the monitor waveguide is disposed at the focus position of the 0-th order diffraction beams obtained from the signals returning from the output side slab-waveguide to the input side slab-waveguide, and the focus positions of the 1-st order diffraction beams are disposed at positions mid way between adjacent ones of the input waveguides.
In this invention, the monitor waveguide is provided such that its ports are disposed at the focus positions of the 0-th order diffraction beams obtained from the signals returned to the input side slab-waveguide side. The focus positions of the higher order diffraction beams of the monitor signals are set mid way between adjacent ones of the input ports. Thus, the quantity of the returned signals inputted in the reverse direction to the input waveguides is reduced.
According to a twentieth aspect of the present invention, there is provided the arrayed waveguide grating according to the eighteenth aspect, wherein the monitor waveguides are disposed alternately with the input waveguides at the input side slab-waveguide.
In this invention, the monitor waveguide are disposed between the respective input waveguides, the waveguides are concentrically disposed around the center of the input side slab-waveguide, 0-th order diffraction monitor signal is inputted to the monitor waveguide and the higher order diffraction beams are focused around these waveguides, reducing the monitor signals in the input waveguide.
According to a twenty-first aspect of the present invention, there is provided the arrayed waveguide grating according to the eighteenth aspect, wherein the input positions of the input side slab-waveguide corresponding to the individual wavelengths of the inputs inputted to the input waveguides are disposed mid way between the 0-th and 1-st diffraction beams returning from the channel waveguide array.
In this invention, wherein the monitor waveguides are disposed mid way between adjacent ones of the focus positions of 0-th and 1-st diffraction beams of the monitor signals returning from the channel waveguide array. With the input waveguide positions and the monitor signal focus positions set such that they are deviated from one another, the monitor signals passing through the input waveguides are reduced.
According to a twenty-second aspect of the present invention, there is provided the arrayed waveguide grating according to the eighteenth aspect, wherein a region covering the positions of the monitor signal ports in the input side slab-waveguide is set such that it does not overlap but separate from a region covering the positions of the input ports.
In this invention, the region covering the positions of the monitor signal ports in the input side slab-waveguide is spaced apart from the region covering the positions of the input waveguides for inputting the individual wavelength signals, thus reducing the effects of the monitor signals inputted to the input waveguides.
According to a twenty-third aspect of the present invention, there is provided the arrayed waveguide grating according to the eighteenth aspect, wherein the signal returning means includes a higher order diffraction beam reflecting mirror disposed in the output side slab-waveguide at the focus position of the higher order diffraction beams, and a signal returning mirror disposed at a position other than the position of the higher order diffraction beam reflecting mirror and the focus position of the 0-th order diffraction beams for returning the signals reflected by the higher order diffraction beam mirror to the side of the input side.
In this invention, unlike the case of reflecting the monitor signal by the sole higher order diffraction beam reflecting mirror disposed at the focus position of the higher order diffraction beams, the reflected signal is further reflected by a signal returning mirror disposed as a different mirror at a position other than the focus position of, for instance, the 0-th or the 1-st order diffraction beam signals to the side of the input side slab-waveguide. Thus, it is possible to reduce the effects of the monitor signals inputted to the input waveguides of the input side slab-waveguide in dependence on the difference between the returning positions.
According to a twenty-fourth aspect of the present invention, there is provided the arrayed waveguide grating according to the eighteenth aspect, wherein the signal returning means includes a signal returning mirror disposed in the output side slab-waveguide at the focus position of the higher order diffraction beams for returning the higher order diffraction beams incident on that position along a path at a signal angle from the optical axis to the side of the input side.
In this invention, the signal returning mirror for returning the higher order diffraction beams along a path at a signal angle from the optical axis to the input side is provided. Thus, it is possible to reduce the effects of the monitor signal inputted to the input waveguides of the input side slab-waveguide in dependence on the difference between the returning positions.
According to a twenty-fifth aspect of the present invention, there is provided the arrayed waveguide grating according to the eighteenth aspect, wherein the signal returning means includes a mirror disposed on one end face of a substrate with the output side slab-waveguide, a first monitor signal waveguide for leading the signal converged on the focus position of the higher order diffraction beams to the afore-mentioned mirror, and a second monitor signal waveguide, which causes the signal reflected by the afore-mentioned mirror to be inputted to the output side slab-waveguide from a position thereof other than the output port thereof and the focus position of the higher order diffraction beams other than the 0-th order for being outputted to the side of the input side.
In this invention, the monitor signal taken out from the output side slab-waveguide is led through the first monitor signal waveguide up to the end face of the substrate, and the signal reflected by the mirror disposed at this position is inputted to the input side from a position other than the output port of the output side slab-waveguide and the position of the higher order diffraction beams other than the 0-th order. Thus, the monitor signal inputted to the input waveguide of the input side slab-waveguide is reduced in dependence on the difference of the position, from which the monitor signal is returned.
According to a twenty-sixth aspect of the present invention, there is provided the arrayed waveguide grating according to the eighteenth aspect, wherein the signal returning means a monitor signal waveguide, which the signal converged on the focus position of the higher order diffraction beams is inputted to and causes the inputted to be inputted to the output side slab-waveguide from a position thereof other than the output port thereof and the focus position of the higher order diffraction beams for being outputted to the side of the input side.
In this invention, for realizing the take-out of the signal converged at the focus position of the higher order diffraction beams and the input of the taken-out signal from a position other than the focus position of the higher order diffraction beams other than the 0-th order, the monitor signal waveguide connecting both the ports is disposed on the substrate.
According to a twenty-seventh aspect of the present invention, there is provided the arrayed waveguide grating according to the eighteenth aspect, wherein the signal returning means includes an optical fiber, which the signal converged on the focus position of the higher order diffraction beams is inputted to and causes the input to be inputted to the output side slab-waveguide from a position thereof other than the output port thereof and the focus position of the higher order diffraction beams for being outputted to the side of the input side.
In this invention, the optical fiber is used in lieu of the monitor signal waveguide used in the preceding case of the invention.
According to a twenty-eighth aspect of the present invention, there is provided an optical communication system comprising: an optical communication means for outputting signals of individual wavelengths as parallel signals; a multiplexer constituted by an arrayed waveguide grating for wavelength multiplexing the signals of the individual wavelengths outputted from the optical communication means; an optical transmission path for transmitting the wavelength multiplexed signal outputted from the multiplexer; a node provided on the optical transmission path and including an arrayed waveguide grating; a demultiplexer constituted by an arrayed waveguide grating for separating the individual wavelength signals from the signal inputted through the optical transmission path and the node thereon; an optical reception means for receiving the individual wave signals separated by the multiplexer; and the multiplexer including a plurality of input waveguides for inputting signals of individual wavelengths in correspondence to these wavelengths, and a slab-waveguide having a wavelength multiplexed signal output port disposed at the focus position of the 0-th order diffraction signals of the signals inputted from the input waveguides through an input side slab-waveguide and a channel waveguide array and monitor signal port disposed at the focus position of higher order diffraction beams other than the 0-th order obtained from the signals inputted from the input waveguides or monitoring the wavelength multiplexed signal.
In this invention, in the line-structure optical communication system for control by monitor signal, which comprises the optical communication means, the multiplexer constituted by the arrayed waveguide grating for wavelength multiplexing the signals of the individual wavelengths sent out from the optical communication means, the optical transmission line for the wavelength multiplexed signal outputted from the multiplexer, the node provided on the optical transmission line and including the arrayed waveguide grating disposed thereon at an adequate position, the demultiplexer constituted by the arrayed waveguide grating for demultiplexing the signal led along the signal transmission path and through the node, and the optical receiver for receiving the signal signals of the individual wavelengths separated by the demultiplexer, the demultiplexer as the constituent is constituted by the arrayed waveguide grating as mentioned before in connection with the first-mentioned case of the invention.
According to a twenty-ninth aspect of the present invention, there is provided an optical transmission system comprising a transmission path loop having a plurality of nodes connected to one another by transmission paths such that a wavelength multiplexed signal is sent out to these transmission paths; the nodes each including a first arrayed waveguide grating for separating signals of individual wavelengths from the inputted wavelength multiplexed signal and a second arrayed wavelength waveguide grating for waveguide wavelength multiplexing the separated signals of the individual wavelengths; the second arrayed waveguide grating having a plurality of input waveguides for inputting signals of individual wavelengths in correspondence to these signals, and a slab-waveguide having a wavelength multiplexed signal output port disposed at the focus position of the 0-th diffraction beams obtained from the signals inputted from the input waveguides through an input side slab-waveguide and a channel waveguide array and a monitor signal port disposed at the focus position of higher order diffraction beams other than the 0-th order obtained from the signals inputted from the input waveguides for monitoring the wavelength multiplexed signal.
In this invention, in the loop-structure optical communication system, which comprises the loop transmission line including a plurality of nodes connected to one another by transmission lines to a loop from for inputting the wavelength multiplexed signal to these transmission lines, the nodes each including the first arrayed waveguide grating for demultiplexing the wavelength multiplexed signal to separate the individual wavelength signals and the second arrayed waveguide grating for wavelength multiplexing the separated individual wavelength signals, the second waveguide array is constituted by the arrayed waveguide grating as mentioned before in connection with the first-mentioned invention.
According to a thirtieth aspect of the present invention, there is provided an optical communication system comprising: an optical communication means for outputting signals of individual wavelengths as parallel signals; a multiplexer constituted by an arrayed waveguide grating for wavelength multiplexing the individual wavelength signals outputted from the optical communication means; an optical transmission path for transmitting the wavelength multiplexed signal outputted from the multiplexer; a node disposed on the optical transmission path and including an arrayed waveguide grating; a demultiplexer for demultiplexing the signal inputted thereto along the optical transmission path and on the node thereon to separate the individual wavelength signals; an optical reception means for receiving the separated individual wavelength signals from the demultiplexer; and the demultiplexer including a plurality of input waveguides and a slab waveguide having a wavelength multiplexed signal output port disposed at the focus position of the 0-th order diffraction beams inputted from the input waveguides through an input side slab-waveguide and a channel waveguide array, a higher order diffraction beam reflecting means disposed at the focus position of higher order diffraction beam positions other than the 0-th order obtained from the signals inputted from the input waveguides for reflecting the higher order diffraction beams to the side of the plurality of input waveguides and one or more monitor signal ports disposed at a position or positions other than the ports of the plurality of input waveguides for inputting a signal or signals reflected by the higher order signal reflecting means.
In this invention, in the line-structure optical transmission system, which comprises the optical communication means, the multiplexer constituted by the arrayed waveguide grating for wavelength multiplexing the individual wavelength signals sent out from the optical communication means, the optical transmission line for outputting the wavelength multiplexed signal outputted from the multiplexer, the node including the arrayed waveguide grating disposed one optical transmission line at an adequate position, the demultiplexer constituted by the arrayed waveguide grating for demultiplexing the signal inputted along the optical transmission line and through the node to separate the individual wavelength signals, and the signal receiving means for receiving the individual wavelength signals separated the demultiplexer, the multiplexer as the constituent is constituted by the arrayed waveguide grating as mentioned before in connection with the third-mentioned invention.
According to a thirty-first aspect of the present invention, there is provided an optical communication system comprising a transmission path loop having a plurality of nodes connected to one another by transmission paths such that a wavelength multiplexed signal is sent out to these transmission paths; the nodes each including a first arrayed waveguide grating for separating signals of individual wavelengths from the inputted wavelength multiplexed signal and a second arrayed wavelength waveguide grating for waveguide wavelength multiplexing the separated signals of the individual wavelengths; the second arrayed waveguide grating having a slab-waveguide which includes a plurality of input waveguides for inputting signals of individual wavelengths in correspondence to these signals, a multiplexed signal output port disposed at the focus position of the 0-th diffraction beams obtained from the signals inputted from the input waveguides through an input side slab-waveguide and a channel waveguide array, a higher order diffraction beam reflecting means for reflecting the higher order diffraction beams to the side of the plurality of input waveguides and a plurality of monitor signal ports disposed at positions other than the port positions of the plurality of input waveguides for inputting the signals reflected by the higher order diffraction beams, and a monitor signal port disposed at the focus position of higher order diffraction beams other than the 0-th order obtained from the signals inputted from the input waveguides for monitoring the wavelength multiplexed signal.
In this invention, in the loop-structure optical communication system, which comprises the loop-structure transmission line including a plurality of nodes connected to one another for inputting the wavelength multiplexed signal to these transmission lines, the nodes each including the first arrayed waveguide grating for demultiplexing the wavelength multiplexed signal to separate the individual wavelength signals, and the second arrayed waveguide grating for wavelength multiplexing the separated individual wavelength signals. The second arrayed waveguide grating is constituted by the arrayed waveguide grating as mentioned before in connection with the third-mentioned arrayed waveguide grating.